An expert system also represents knowledge symbolically as sets of symbols that stand for problem concepts. In AI jargon symbol is a string of characters that stands for some real world concept. To solve a problem an experts system manipulates these symbols rather than performing standard mathematical computations. This is not to say that expert systems don't do math rather the emphasis is on manipulating symbols. Also experts can take a problem stated in some arbitrary manner and convert it to a form that lends itself to a fast or efficient solution. This problem reformulation capability is something experts systems need to make their skill level closer to that of human experts.